It’s summer here in Sweden, which means a lot of sun, heat, and… well, right now, rain, but hopefully things will get better.
Credits: Silvia Man/imagebank.sweden.se
As every year, we try to enjoy it as much as possible. That means that some of us are taking off for well-deserved vacations. During the coming month, Bitcraze will be run by a skeleton crew of people.
That means that the office will get slower too. Now, keep in mind that in a company made by only 6 persons, 3 people going on holidays is taking half the workforce – so the remaining men and women are here to keep things afloat. We will still ship the orders regularly – in a huge part thanks to your new and improved packing system– and answer emails, helping you on Github discussions etc… on a regular basis. But our response time may be slower than usual – and some things will have to be postponed until the right person can get to it. We will, of course, always tell you what’s happening, and keep going with the Monday blogposts.
For us that are in the office, it is also the chance to focus on more personal projects. Often during the summer, when our colleagues are away, we grab the opportunity to develop ideas and projects that we usually don’t prioritize. Last summer, for example, Kimberly dig deeper into ROS2. I myself will try to make some changes to the office itself. We will also try to clean up- not only the office itself, but fixing various bugs that usually don’t get the highest priority. In general, we try to have a clean slate before things start to get back up again.
We hope that you can also enjoy a slower summer and some vacations!
Today, Lennart Bult from Emergent Swarns presents us with this project of a 24/7 swarming demo. Enjoy!
Over the last few months our team has been working on creating a 24/7 swarming demo. Initially tasked by Guido de Croon and Chris Verhoeven from TU Delft MAVLab and the TU Delft Robotics Institute, we set out to find our way within the Crazyflie ecosystem to gradually increase the size and capabilities of the swarm. In this article we will first talk about some of the work and methods that we used. After that, we will introduce the TU Delft Science Centre Swarming Lab and talk about some applications of swarming drones.
Developing the 24/7 swarm
The project started in February with the goal of creating a physical swarm capable of real-time collision avoidance with drones and static obstacles. We started out with three drones equipped with the Flow Deck, and by setting them up in a clever way we could perform the first collision avoidance and landing tests. We were impressed with the performance we got out of the Flow Deck, however, eventually, it is mostly a battle against the drift of the position estimate, that is, we could increase some of the margins on the collision avoidance only so far before we would either fly out of the test zone or collide with another drone. Luckily with short test flights, we were able to see some of the flaws in our algorithms and correct them before testing with the new setup.
Setup after the first expansion to eight drones.
After a few weeks of testing we got approved for the first swarm expansion, five more drones and a Lighthouse positioning setup. This is when we could do our first real tests with the collision avoidance algorithm, which, much to our own surprise, worked on the first try. This is also when we first posted a project update on LinkedIn. There were however a lot of bugs that still needed to be worked out, and a lot of system experience still to be gained. After flying for a bit longer we noticed that some of the drones would flip quite often, which is when we discovered that we needed the thrust upgrade to control the additional weight of the larger battery and charging deck.
For the charging setup we took inspiration from the Bitcraze IROS 2022 demo; we 3D printed sloped landing pads that we tape onto a wireless charger. After a few iterations we landed on a design that uses minimal printer resources and allows the Crazyflie to land a bit off-center. This last feature turned out to be quite useful considering the large amount of destabilizing airflow that is generated by 40 drones. After receiving the last order of drones we also expanded the charging setup, which at this point takes up quite a bit of floor space. There are some ideas to create a vertical landing pad stack, which would bring the additional challenge of missing the landing pad not being an option.
All 40 drones recharging before their next flight.
After prototyping the charging setup and building confidence with the initial setup, we were confident enough in our system capabilities to expand it to the point where a continuous demo of 5-8 drones is possible. Although the system integration of the previous expansion went without much trouble, we did encounter a few issues when expanding to 40 drones. The first issue of which was radio communication, we noticed that a delay in the radio communication would be present if we increased the update rate above a certain level for a specific number of drones per radio. The second issue we encountered were performance drops related to the violation of certain bounds in the collision avoidance algorithm. These two issues were very difficult to debug since it was not immediately obvious where the source of the issue was.
The third and last major issue was the increase in destabilizing airflow of 40 drones compared to 8. With 40 drones there is a noticeable breeze when you stand next to the drone cage, which is nice for summertime, but not so nice when drones need to land in a tight-packed configuration. To combat this issue there is a limit to the amount of drones that can land at the same time. There is also a minimum separation distance between two active landing pads, which reduced the severity of the induced turbulence. There are still ongoing efforts to increase the landing success rate, which is currently affected by drones running out of power during the landing procedure.
To control and monitor the swarm we designed a custom GUI, an impression of which you can see below. Although some of the buttons are still a work in progress, there are a lot of features that have already proven very useful, especially when testing a new feature.
V1 of the graphical user interface developed for the 24/7 swarm.
The code base that we created for the swarm will be largely open-sourced (only the collision avoidance will not be open-source) to provide researchers all around the world with the possibility to setup their own Crazyflie swarm for research. You can find the repository through this link. Note that the documentation and code base are still under development and might contain bugs/errors.
Human interaction
After creating all functionality to provide a continuously operating swarm demo, it was time to work on some of our stretch goals: 1. walking through the swarm whilst it is operating and 2. controlling the swarm using our arms. In the image below you can see an impression of precisely this functionality. The drones are following the operator’s gesture commands whilst performing live collision avoidance with an operator.
Team member Seppe directing the 40 drone swarm, see the full video here.
This demo requires multiple techniques and hardware elements working together to create a relatively low-latency, human-controlled swarm. We used a Kinect-like 3D sensor to perform human pose estimation, we subsequently used this data to create a dynamic obstacle in our collision avoidance software. An important element to consider here is the synchronization of the Lighthouse- and 3D sensor coordinate frames, i.e. without proper calibration the human will not be correctly positioned with respect to the drones and the drones will crash into the human. The interaction between the swarm control software and the human gesture commands also requires careful consideration, proper tuning is required to ensure a responsive system that is reliable and not too aggressive.
TUD Science Centre Swarming Lab
The next step in this project will be to set up the swarm at its new location, the TU Delft Science Centre. Here, the swarm will first and foremost be visible as a public demo, showcasing the capabilities of TU Delft state-of-the-art swarming research. There will also be a focus on developing the swarm as a research platform. This will allow TU Delft students and researchers to extend swarm functionalities and test their theory on a physical swarming system. Besides demos and academic research, there will also be worked on developing educational applications across the full educational board (primary school, high school and applied education). If you are interested in working on, or collaborating with the swarming lab on any of the above-mentioned tasks, feel free to email the lab management at operations.swarminglab@tudelft.nl.
The TU Delft Swarming Lab setup with 40 drones and charging pads for continuous operations and research.
Applications of Swarming
There are a lot of potential use-cases for fully autonomous drone swarms, ranging from indoor applications such as warehouse monitoring and factory inspection to outdoor applications such as search and rescue and surveillance. In our opinion, the true potential of drone swarms lies in applications where there is a significant need for a scalable system with a lot of built-in redundancy. A lot of additional use cases open up when we consider fully onboard autonomous systems, where the full benefits of decentralized swarming can be utilized. Currently, the size of drones needed to achieve such feats is quite large, though maybe in a few years, we could see more and more being done on drone platforms such as the Crazyflie.
A swarm inspection of an F-16 Fighting Falcon at Deltion College in Zwolle, the Netherlands.
An interesting area of application for drone swarms could be in the inspection of aircraft. Drone swarms provide a scalable and flexible means to perform a fast inspection of aircraft across an entire airfield or military base. To showcase that this can be done with any size of drone, we went to Deltion College in Zwolle to perform a mock inspection of an F-16 fighter jet. Above you can see an impression of the inspection. Another area of application is search and rescue, where there is a need for systems that can find people or objects of interest in unknown and cluttered environments. Furthermore, the area that needs to be searched is usually very large and sometimes difficult to travel on foot. A drone swarm could provide fast and reliable coverage of the area of interest, whilst providing full data traceability. Seppe and Lennart will work on creating drone swarms for these use cases with the start-up Emergent Swarms.
In our ROS-aerial community working group, we had a meeting a few weeks ago to discuss education and tutorials within Aerial Robotics (see the ROS discourse thread here). The general conclusion was that there should be more courses and tutorials since the learning curve is too steep. But… is that actually the case? According to a LinkedIn post by Kimberly, asking for suggestions, we found out that might not be true! There are loads of tutorials out there! So in this blog post, we will provide an overview of the suggested tutorials and the ones that have materials available online.
Stable diffusion with prompt ‘A drone flying in front of a school blackboard’
Online books
One of the first suggestions was to explore the online free book titled ‘Small Unmanned Aircraft: Theory and Practice.’ This book has been written by Randy Beard and Tim McLain of Brigham Young University, and it covers everything from the absolute basics of coordinate frames and quadrotor dynamics to path planning and cameras. It is a must-read for anybody starting in UAVs and Aerial robotics.
Here are some suggestions for courses specifically focused on Aerial Robotics. These received the most recommendations! Many universities have made their courses available online, accessible to anyone interested.
Coursera offers the ‘Robotics: Aerial Robotics’ course as part of the Robotics specialization. Taught by Prof. Vijay Kumar from Penn University, this 4-week course covers the mechanics and control of aerial vehicles using Matlab. It starts from 1 dimension and gradually progresses to the 3rd dimension in simulation. The course is part of a paid educational program, but you can audit the lessons for free.
Udacity has been offering a course on Aerial Vehicles for quite some time. The lessons are taught by top names in the industry and cover key aspects of Aerial Robotics, such as motion planning, controls, and estimation, with lab assignments involving a real drone. The course duration is 4 months, and access is available for a fee.
The University of Maryland offers a course on Autonomous Aerial Robotics, making all videos, slides, and assignments available. Taught by Nitin J. Sanket and Chahat Deep Singh, the course covers everything from basic control and dynamics to full autonomy. It’s a comprehensive resource for aerial robotics. The course utilizes the Parrot Bebop 2.0, and while a Mocap system is required, you may explore the possibility of adapting the course to a different platform.
Additionally, there’s the course ‘Applied Control System 3: UAV Drone (3D Dynamics & Control)’ which is part of a series by Mark Misin. This course delves deep into the dynamics, control, and modeling of quadrotors.
Here are some suggestions for courses that focus on robotics but utilize UAVs/drones to demonstrate the implementation of the studied materials.
‘Visual Navigation For Autonomous Vehicles’ is a course available on MIT Open Courseware, taught by Prof. Luca Carlone. As the name implies, the course primarily focuses on autonomous navigation for any autonomous vehicle. It includes exercises where students implement vision algorithms on both ground robots and drones. Additionally, the course covers working with ROS and applying the knowledge to a simulated drone in Unity.
The ‘Bio-inspired Robotics’ course at the University of Washington, led by Prof. Sawyer Fuller, explores the realm of drawing inspiration from nature rather than reinventing the wheel. It covers various robots inspired by creatures capable of swimming, walking, hopping, and of course, flying. Lab assignments in this course involve working with a Crazyflie drone.
Brown University offers a course called ‘Introduction to Robotics,’ taught by Prof. Stefanie Tellix. While the introduction covers generic robotics, the focus of the full course is on building and programming the Duckiedrone. The course dives straight into autonomy and also teaches students how to work with ROS.
Princeton University (see this blogpost) have also decided to release their ‘Intro to Robotics’ lectures and materials for the public. Can’t believe I forgot this one!
If you’d like to start hands-on right away, here are a couple of suggestions for YouTube tutorials or series about aerial robotics.
Drone Programming with Python: This popular tutorial/course teaches viewers how to program a real drone using Python with the DJI Tello. It offers a great opportunity for anyone looking for a short and enjoyable project to undertake, especially on a rainy day, while still working with a real platform.
Intelligent Quads YouTube Channel: This channel is entirely dedicated to creating autonomous UAVs, covering topics from Ardupilot to MAVlink to ROS and Gazebo. It appears to be a valuable resource for beginners in the field of autonomous UAVs.
There are some extra recourses for you to also take a look at.
University of Twente UAV Centre: The University of Twente has created a portal with a variety of UAV-related courses. You can find a wealth of information and educational materials on their website. Link: https://www.itc.nl/facilities/centres-of-expertise/uav-centre/
Self-Driving Car Specialization: If you are interested in learning more about SLAM (Simultaneous Localization and Mapping) and sensors, this specialization is tailored for self-driving cars but the theory can be useful for drones as well. Link: https://www.coursera.org/specializations/self-driving-cars
Autonomous Navigation for Flying Robots: This older course is still highly relevant for anyone interested in autonomous navigation for flying robots. It offers valuable insights and knowledge. Link: https://www.edx.org/course/autonomous-navigation-for-flying-robots
Drone Dojo: For those looking to build their own drones, Drone Dojo provides useful instructions and courses to get started on DIY drone projects. Link: https://dojofordrones.com/
Indeed, it appears that there are plenty of courses and tutorials available for people interested in getting started with aerial robotics. The range of resources is vast, and it’s possible that we might still be missing some, which could lead to a part 2 of this blog post in the future! And perhaps also we would need to delve into these to see why the learning curve is considered steep. However, aerial robotics is not an easy subject anyway so perhaps it is good to start from the basics. Nevertheless, this compilation should provide a solid starting point for anyone eager to delve into the world of aerial robotics. A major thank you to everyone who has contributed so far (linked to in the original LinkedIn post); your valuable input has made this possible!
Did you know that all the items you receive when you place an order are actually from the Bitcraze office? In the beginning, we had the shipping handled by a third party, but it caused some problems and we decided to have this side of the business closer to us- namely, right here at the office in Malmö.
Our packing area
We have a “warehouse” with our products in our flight lab, and thrice a week someone takes the order, fulfills them, packs them and hands them over to FedEx. So how does this work exactly?
Well, a lot of this is possible thanks to our internal system, a Raspberry Pi, and three printers. When we fulfill your order, we have a lot of things to take into account. The weight of the shipment, the number of batteries it contains, what kind of shipment you ordered, the destination country, the kind of labels that are needed…. Thankfully, everything is handled by our internal system, and with one click we have everything we need. If you booked a FedEx shipment, our API books the FedEx shipment immediately and prints it.
We actually have three different printers. One prints the packaging list that we put in your package, along with one that helps us know what to pack. It’s a regular, office printer. The second one prints the shipping label. A third one is used for packages that contain batteries: those are, of course, heavily regulated, and we need to label them correctly to ensure the safest way to transport them. Hence the need for a third printer, which prints somewhat smaller labels. Some of us actually followed a course to be able to handle a shipment containing more than 2 spare batteries per drone… It is then considered a “Dangerous Goods” shipment by FedEx and has to be treated, labeled, and sent following a precise protocol.
Here they are in action:
Once everything is printed, the “only” thing left is to actually pack the box! It’s what takes up the most time. We select your items (without forgetting the stickers!), place them in the box that should be the right size, and try to pack everything so that it is safe to transport to the other side of the world. We then hand everything to FedEx which takes it from there. We try, as much as possible, to ship within 3 business days. That usually means packing and sending on Mondays, Wednesdays, and Fridays – though conferences or holidays can shake this up a bit.
The obvious advantage of having everything set up here is that we have a lot more control over this important side of the business. We have an eye on stock, on how the package looks like, and have an idea of where we actually send our products! The downside is that it takes a lot of time away from development. But these past couple of months, we’ve done a lot to improve our experience while packing. Those include an already filled-out Customs Notice for postal packages and a quicker way to handle packages that have more than 2 spare batteries. But the biggest change is that we have hired someone to help us part-time. Sofia started a week ago and she already has helped take care of the shipping part of Bitcraze. So welcome, Sofia, to the Bitcraze team!
We are happy to announce that we are working on a new upgrade battery for the Crazyflies! It will soon hit production and hopefully, keeping our fingers crossed, it will arrive in our stock in early 2023-Q4.
The upgrade battery is based on the “Tattu 350mAh 3.7V 30C 1S1P” cell and with some additional great features:
Protection Circuit Module (PCM) to protect against short circuits, overcharge, over discharge etc.
Gold-plated connectors for lower contact resistance.
Shrink wrap around connector for better rigidity.
Cool Bitcraze matched graphics.
And if we list the benefits compared to the stock Crazyflie battery:
Higher current capabilities, 30C burst current, that is >10 Amp.
350mAh instead of 250mAh
Higher energy density, ~130 Wh/kg instead of ~105 Wh/kg
There are some drawbacks too:
It is ~1 mm thicker and does not fit well with all deck boards and the short or medium size pin headers. We will release longer pin headers at the same time though.
Price will be higher
~1.5 grams extra weight
With this upgrade battery, you will experience longer flight times, more “punch” during acceleration and it is great combined with the thrust upgrade kit!
As you may have noticed from the recent blog posts, we were very excited about ICRA London 2023! And it seems that we had every right to be, as this conference had the highest number of Crazyflie related papers compared to all the previous robotics conferences! In the past, the conferences typically had between 13-16 papers, but this time… BOOM! 28 papers! In this blog post, we will provide a list of these papers and give a general evaluation of the topics and themes covered so far.
So here some stats:
ICRA had 1655 papers accepted (43 % acceptance rate)
28 Crazyflie papers (25 proceedings, 1 RA-L, 1RO-L, 1 late breaking result postor)
Haven’t included the workshop papers this time (no time)
The major topics we discovered were swarm coordination, safe trajectory planning, efficient autonomy, and onboard processing
Additionally, we came across a few notable posters, including one about a grappling hook for the Crazyflie [26], a human suit that allows for drone control [5], the Bolt made into a monocopter with a Jetson companion [16], and a flexible fixed-wing platform driven by a barebone Crazyflie [1]. We also observed a growing interest in aerial robotics with approximately 10% of all sessions dedicated to UAVs. Interestingly, 18 out of the 28 Crazyflie papers were presented in non-UAV specialized sessions, such as multi-robot systems and vision-based navigation.
Swarm coordination
Swarms were a hot topic at ICRA 2023 as already noticed by this tweet of Ramon Roche. We had over 10 papers dedicated to this topic, including one that involved 16 Crazyflies [9]. Surprisingly, more than half of the papers utilized multiple Crazyflies. This already sets a different landscape compared to IROS 2022, where autonomous navigation took center stage.
In IROS 2022, we witnessed single-drone gas mapping using a Crazyflie, but now it has been replicated in the Webots simulation using 2 Crazyflies [23]. Does this imply that we might witness a 3D gas localizing swarm at IROS 2023? We can’t wait.
Furthermore, we came across a paper [11] featuring the Bolt-based platform, which demonstrated flying formations while being attached to another platform using a string. It presented an intriguing control problem. Additionally, there was a work that combined safe trajectory planning with swarm coordination, enabling the avoidance of obstacles and people [12]. Moreover, there were some notable collaborations, such as robot pickup and delivery involving the Turtlebot 3 Burger [22].
Given the abundance of swarm papers, it’s impossible for us to delve into each of them, but it’s all very impressive work.
Safe trajectory planning and AI-deck
Another significant buzzword at ICRA was “safety-critical control.” This is important to ensuring safe control from a human interface [15] and employing it to facilitate reinforcement learning [27]. The latter approach is considered less “safe” in terms of designing controllers, as evidenced by the previous IROS competition, the Safe Robot Learning Competition. Although the Crazyflie itself is quite safe, it makes sense to first experiment with safe trajectories on it before applying them to larger drones.
Furthermore, we encountered approximately three papers related to the AIdeck. These papers covered various topics such as optical flow detection [17], visual pose estimation [21], and the detection of other Crazyflies [5]. During the conference, we heard that the AIdeck presents certain challenges for researchers, but we remain hopeful that we will see more papers exploring its potential in the future!
List of papers
This list not only physical Crazyflie papers, but also papers that uses simulation or parameters of the Crazyflie. This time the workshop papers are not included but we’ll add them later once we have the time
Enjoy!
‘A Micro Aircraft with Passive Variable-Sweep Wings’ Songnan Bai, Runze Ding, Pakpong Chirarattananon from City University of Hong Kong
‘Onboard Controller Design for Nano UAV Swarm in Operator-Guided Collective Behaviors’ Tugay Alperen Karagüzel, Victor Retamal Guiberteau, Eliseo Ferrante from Vrije Universiteit Amsterdam
‘Multi-Target Pursuit by a Decentralized Heterogeneous UAV Swarm Using Deep Multi-Agent Reinforcement Learning’ Maryam Kouzehgar, Youngbin Song, Malika Meghjani, Roland Bouffanais from Singapore University of Technology and Design [Video]
‘Inverted Landing in a Small Aerial Robot Via Deep Reinforcement Learning for Triggering and Control of Rotational Maneuvers’ Bryan Habas, Jack W. Langelaan, Bo Cheng from Pennsylvania State University [Video]
‘Ultra-Low Power Deep Learning-Based Monocular Relative Localization Onboard Nano-Quadrotors’ Stefano Bonato, Stefano Carlo Lambertenghi, Elia Cereda, Alessandro Giusti, Daniele Palossi from USI-SUPSI-IDSIA Lugano, ISL Zurich [Video]
‘A Hybrid Quadratic Programming Framework for Real-Time Embedded Safety-Critical Control’ Ryan Bena, Sushmit Hossain, Buyun Chen, Wei Wu, Quan Nguyen from University of Southern California [Video]
‘Distributed Potential iLQR: Scalable Game-Theoretic Trajectory Planning for Multi-Agent Interactions’ Zach Williams, Jushan Chen, Negar Mehr from University of Illinois Urbana-Champaign
‘Scalable Task-Driven Robotic Swarm Control Via Collision Avoidance and Learning Mean-Field Control’ Kai Cui, MLI, Christian Fabian, Heinz Koeppl from Technische Universität Darmstadt
‘Multi-Agent Spatial Predictive Control with Application to Drone Flocking’ Andreas Brandstätter, Scott Smolka, Scott Stoller, Ashish Tiwari, Radu Grosu from Technische Universität Wien, Stony Brook University, Microsoft Corp, TU Wien [Video]
‘Trajectory Planning for the Bidirectional Quadrotor As a Differentially Flat Hybrid System’ Katherine Mao, Jake Welde, M. Ani Hsieh, Vijay Kumar from University of Pennsylvania
‘Forming and Controlling Hitches in Midair Using Aerial Robots’ Diego Salazar-Dantonio, Subhrajit Bhattacharya, David Saldana from Lehigh University [Video]
‘AMSwarm: An Alternating Minimization Approach for Safe Motion Planning of Quadrotor Swarms in Cluttered Environments’ Vivek Kantilal Adajania, Siqi Zhou, Arun Singh, Angela P. Schoellig from University of Toronto, Technical University of Munich, University of Tartu [Video]
‘Decentralized Deadlock-Free Trajectory Planning for Quadrotor Swarm in Obstacle-Rich Environments’ Jungwon Park, Inkyu Jang, H. Jin Kim from Seoul National University
‘A Negative Imaginary Theory-Based Time-Varying Group Formation Tracking Scheme for Multi-Robot Systems: Applications to Quadcopters’ Yu-Hsiang Su, Parijat Bhowmick, Alexander Lanzon from The University of Manchester, Indian Institute of Technology Guwahati
‘Safe Operations of an Aerial Swarm Via a Cobot Human Swarm Interface’ Sydrak Abdi, Derek Paley from University of Maryland [Video]
‘Direct Angular Rate Estimation without Event Motion-Compensation at High Angular Rates’ Matthew Ng, Xinyu Cai, Shaohui Foong from Singapore University of Technology and Design
‘NanoFlowNet: Real-Time Dense Optical Flow on a Nano Quadcopter’ Rik Jan Bouwmeester, Federico Paredes-valles, Guido De Croon from Delft University of Technology [Video]
‘Adaptive Risk-Tendency: Nano Drone Navigation in Cluttered Environments with Distributional Reinforcement Learning’ Cheng Liu, Erik-jan Van Kampen, Guido De Croon from Delft University of Technology
‘Relay Pursuit for Multirobot Target Tracking on Tile Graphs’ Shashwata Mandal, Sourabh Bhattacharya from Iowa State University
‘A Distributed Online Optimization Strategy for Cooperative Robotic Surveillance’ Lorenzo Pichierri, Guido Carnevale, Lorenzo Sforni, Andrea Testa, Giuseppe Notarstefano from University of Bologna [Video]
‘Deep Neural Network Architecture Search for Accurate Visual Pose Estimation Aboard Nano-UAVs’ Elia Cereda, Luca Crupi, Matteo Risso, Alessio Burrello, Luca Benini, Alessandro Giusti, Daniele Jahier Pagliari, Daniele Palossi from IDSIA USI-SUPSI, Politecnico di Torino, Università di Bologna, University of Bologna, SUPSIETH Zurich [Video]
‘Multi-Robot Pickup and Delivery Via Distributed Resource Allocation’ Andrea Camisa, Andrea Testa, Giuseppe Notarstefano from Università di Bologna [Video]
‘Multi-Robot 3D Gas Distribution Mapping: Coordination, Information Sharing and Environmental Knowledge’ Chiara Ercolani, Shashank Mahendra Deshmukh, Thomas Laurent Peeters, Alcherio Martinoli from EPFL
‘Finding Optimal Modular Robots for Aerial Tasks’ Jiawei Xu, David Saldana from Lehigh University
‘Statistical Safety and Robustness Guarantees for Feedback Motion Planning of Unknown Underactuated Stochastic Systems’ Craig Knuth, Glen Chou, Jamie Reese, Joseph Moore from Johns Hopkins University, MIT
‘Spring-Powered Tether Launching Mechanism for Improving Micro-UAV Air Mobility’ Felipe Borja from Carnegie Mellon university
‘Reinforcement Learning for Safe Robot Control Using Control Lyapunov Barrier Functions’ Desong Du, Shaohang Han, Naiming Qi, Haitham Bou Ammar, Jun Wang, Wei Pan from Harbin Institute of Technology, Delft University of Technology, Princeton University, University College London [Video]
‘Safety-Critical Ergodic Exploration in Cluttered Environments Via Control Barrier Functions’ Cameron Lerch, Dayi Dong, Ian Abraham from Yale University
We’re happy to announce that there is a new release of the software for the Crazyflie ecosystem! The new release is called 2023.06 and is available for download on github or through the python client.
Major changes
The main addition is an extended supervisor framework and updated arming functionality.
Extended supervisor framework
The purpose of the supervisor is (will be) to keep an eye on the Crazyflie and make sure that everything is fine. If it detects a problem it can take action to hopefully handle the situation in a way that is better for the Crazyflie as well as people close by. The supervisor taps into the stabilizer loop and has the power to take control of the motors when needed.
The current version actually behaves very much like the previous version, but the underlying framework has been re-written to enable better handling in the future. There are now well defined states that the Crazyflie goes through for preflight checks, when flying and after landing.
Arming
Basic arming functionality has been added, mainly intended for larger platforms with brushless motors. A manual action is required after preflight checks have passed, to let the Crayflie know that a human is in control. If the system is not armed, it is not possible to fly.
Arming is required by default for the Bolt platform. For the Crazyflie 2.X, there is an auto-arming feature that immediately arms the platform when the preflight checks have passed, that is it works like it used to do.
If you use a BigQuad deck, auto-arming will also be enabled by default (as it uses the Crazyflie 2.X platform) and the firmware should be rebuilt with the MOTORS_REQUIRE_ARMING kbuild config flag set to enable manual arming.
The arming functionality is built on top of the supervisor.
Updates to the python client
An arming button has been added to the flight tab in the client to support the new arming functionality.
An emergency stop button has also been added to the top of the client window that shuts down the motors immediately.
Updates to the python library
A new CRTP message has been added to arm/disarm the system. The CRTP version has been updated to version 6.
Note, if you are controlling a Bolt from a script (or any other platform with arming enabled) you have to send an arming message to the platform before you can fly.
Release details
The following versions were released. See each release for details.
As mentioned in a previous blog post, we have a both at ICRA in London this week. If you are there too, come and visit us in booth H10 and tell us what you are working on!
Barbara and Arnaud is getting the booth ready
We are showing our live autonomous demo and our products in the booth, including the flapping drone Flapper Nimble, don’t miss it!
The autonomous demo
The decentralized autonomous demo that we are showing is based on technologies in the Crazyflie ecosystem. The general outline is that Crazyflies are autonomously flying in randomized patterns without colliding. The main features are:
Positioning using the Lighthouse positioning system, all positioning estimation is done in the drone. The Lighthouse positioning system provides high accuracy and ease of use.
Communication is all peer-to-peer, no centralized functionality. Each Crazyflie is transmitting information about its state and position to the other peers, to enable them to act properly.
Collision avoidance using the on-board system without central planing. Based on the position of the other peers, each Crazyflie avoids collisions by modifying its current trajectory.
Wireless charging using the Qi-deck. When running out of battery, the Crazyflies go back to their charging pads for an automatic re-fill.
The App framework is used to implement the demo. The app framework provides an easy way of writing and maintaining user code that runs in the Crazyflie.
We are happy to answer any questions on how the technology works and implementation details. You can also read more about the demo in the original blog post by Marios.
Developer meeting
The next developer meeting is next week, Wed June 7 15:00 CEST and the topic will be the demo and how it is implemented. If you want to know about any specific technologies we used, how it is implemented or if you are just curious about the demo in general, please join the developer meeting. We will start with a presentation of the different parts of the demo, and after that a Q&A. As always we will end up with a section where you can ask any question you like related to our ecosystem. Checkout this announcement on our discussion platform for information on how to join.
If you have been following the ROS Discourse on a regular basis, you might have seen a bit more activity on the Aerial Vehicles category than usual. We very recently started an Aerial Robotics Working Group in collaboration with Dronecode Foundation! It will be a community-driven working group initially, but we will hold biweekly meetings on Wednesday at 2:00 PM UTC, and build up a community members and gather information on the ROS Aerial community’s Github organization. This blogpost aims to explain how this working group came to light, what our current plans are and how you can participate.
How did it all begin?
There are actually quite some aerial enthusiasts out there dwelling in the ROS crowd, which became evident when 20-30 people showed up at the impromptu ROScon 2022 aerial roboticists meetup. This was also our first experience with ROScon as Bitcraze, and I (Kimberly) absolutely loved it. The idea popped to be able to be more active in the amazing ROS community, which we started doing with helping out more with the Crazyswarm2 project (see this blogpost) and giving a presentation about it as well. However, we did notice that there wasn’t as much online chatter about Aerial Vehicles on the ROS communication channels. Yes, the Embedded ROS working group led by eProsima (responsible for MicroROS) has done some really cool demos with Crazyflies! And the same goes for any other aerial project, that has probably contributed to some of the other staple projects like NAV2. But there aren’t any working groups that are specific for aerial robotics.
Since PX4 led by Dronecode foundation had similar ambitions to be emerged into the ROS family, since we met in person at the very same ROScon last year, we started talking about possibly starting up a working group. This started with us reaching out to the ROS community for interest with this ROS discourse post and after 25 and more replies, the obvious thing was to set up an first explorative meeting. About 30 people showed up to this, so the message was clear: yes, there is a demand for guidance, structure, and information in the ROS community regarding aerial robotics. Thus, the aerial robotics working group was born!
Current state and plans
One of the observed issues is that we have noticed that is happening is that there there are numerous projects and information about aerial robotics, and perhaps too much. That is because aerial robotics consists of a huge variety of robotic systems in different forms like multicopters or even monocopters (like in the blogpost here) but also hybrid VTOL vehicles, mini blimps (for example this hack we done) and so many more. But as you probably know, aerial vehicles come with their own set of challenges that distinguish them from ground robots, like instability, aerodynamics, and limitations related to their lift capabilities. Therefore, it offers an interesting platform for control theory, autonomy, and swarming and as a result several ROS-related projects have emerged, such as Crazyswarm2, Aerostack2, Kumar Robotics Autonomy Stack and, Agilicious. Moreover, even though a standard ROS interface for aerial robotics has been created some years ago, it has not been enforced or updated since. And also, although courses and tutorials can be found here and there scattered around on multiple projects and autopilot websites to get started with aerial robotics in ROS, but many have found the learning curve to be quite steep and usually don’t know where to start.
Due to the vast amount of systems, software, projects and information out there, we decided to gather all this information in one centralized location as an Aerial Robotics landscape instead of scattering it across various aerial robotics resources, of which we have created a simple repository with markdown files. The idea is to fill this in little by little by info that we get from the working group discussions or other input of users, or research done by ourselves. For that, we will facilitate biweekly meetings, where users will present about their project (like our last meeting about Aerostack 2) or where we engage in discussions on various aerial robotics topics (like Aerial Autonomy stacks in the startup meeting).
Future ambitions
Currently, we don’t have a specific end goal or main project in mind, as we are right at the start of the first discussions and information gathering. That is also why it will be considered a ‘community driven’ working group after some emails back and forth with Open Robotics Foundation, until we reach a stage where the landscape is adequately developed to establish specific development goals. and set up various subprojects for communication, autonomy, platforms and/or education. Additionally, incorporating direct communication protocols within swarms could be of interest, as these are a common use case within aerial robotics. Once we have established more specific development goals, we can apply to be an official ROS working group, and collaborate with other workgroups on overlapping projects. From our perspective, it would be more beneficial for the ROS ecosystem not to create a standalone aerial stack, but enhance the integration of other stacks with aerial vehicles.
Join us!
Currently I (Kimberly) representing Bitcraze and Ramon Roche from Dronecode Foundation will be in the ‘lead’ of the Aerial working group, although we prefer to act as facilitators rather than imposing our own direction. We will try our best not to geek out too much on PX4 and/or Crazyflies alone, so therefore anybody’s input will be crucial! So if you’d like to levitate ROS to new heights, come and join our meetings! Our next meeting is scheduled for Wednesday the 24th of May (2 pm UTC), and you can find the information on this ROS Discourse thread. We hope to see you there!
In just about 2 weeks, it’s ICRA 2023, which, as you could guess from the title of the post, is in London. The ExCel venue will welcome the world’s top academics, researchers, and industry representatives from May 29 to June 2nd, and that’s something we don’t want to miss.
ICRA is a conference that we hold dear and attended quite a few times – whether in person or online. We’ll be holding a booth there so don’t hesitate to pass by to say hello and see our demo!
We will be using the same demo as the one from IROS 2022; a fully decentralized swarm with the Lighthouse system. What we changed is that now we will be using the Crazyradio 2.0. We’re working on updating the demo and seeing what can be improved in the time we have before the conference. As a bonus, we plan to bring some prototypes and surprises; just to show off all the work we’ve been doing since our last conference in Japan. We will also have Matej Karasek, our partner from Flapper Drones with us in the booth! A good occasion to see his Nimble + in action and ask him all your questions.
Additionally, on Friday afternoon there will be a half-day workshop called ‘The Role of Robotics Simulators for Unmanned Aerial Vehicles’ that we helped organized. This workshop gathers researchers who have struggled to find, customize, or design a robotic simulator for their own purposes or specific application; so don’t hesitate to join if you’ve worked (or plan to) with drone simulation. All the information are here, be sure to sign up for it at your ICRA registration if you’re interested. It can also be attended by a stream by signing up for the virtual ICRA conference.
So we hope to see you in London, at booth H10 for good discussions, interesting conversations, and eventually a cup of tea!
